Algae

Algae are a diverse group of organisms that can be found in both terrestrial and aquatic habitats. In turfgrass systems, both eukaryotic and prokaryotic algae can be present, but the most common inhabitants are prokaryotic cyanobacteria, also known as “blue-green algae.” Blue-green algae are characterized by their ability to photosynthesize using chlorophyll a and phycobilin pigments.

Credit: PACE Turf

 

Causal agents

Prokaryotic cyanobacteria, commonly known as blue-green algae, are the most common algae in turfgrass systems.

 

Primary Hosts

All turfgrasses are susceptible to algae infestations, but turfgrass grown on putting greens are most susceptible.

 

Disease Cycle

Algae can persist in turfgrass foliage, forming filaments called trichomes and producing mucilaginous sheaths.

Algal growth can be influenced by the following factors:

  • temperature
  • humidity
  • soil moisture,
  • mowing height

 

Epidemiology

Algal growth is most aggressive in warm, humid climates, poorly drained areas, and where mowing heights are low.

 

Symptoms

Algal growth can create a slimy or slimy appearance on turfgrass, often seen as green or bluish-green mats. Excessive algal growth can result in indirect injury to turfgrass by impeding air and water movement and reducing soil aeration and drainage.

 

Credit: John Kaminski/Penn State University

 

Figure 15.2.1: Algae symptoms can range from (a) thinned or weak turf to (b) discolored turf in highly trafficked areas. In some cases, (c) yellow spots may appear as a malady of unknown etiology that is attributed to the activity of cyanobacteria. (d) In severe cases, the algae clogs up entire surfaces and forms a crust that is difficult to grow grass within.

 

 

Signs

Blue-green algae are characterized by the presence of filaments (trichomes) and mucilaginous sheaths. Algal mats may appear slimy and can be observed on the turfgrass surface or in the soil.

 

Credit: John Kaminski/Penn State University

 

Figure 15.2.2: Algae manifests within the canopy of the turfgrass and under low light situations will “climb” to the top of leaves in search of sunlight. (a&b) The sign of algae is a black or dark green mucilage like material. (c) Under a microscope, the green photosynthesizing nature of the cyanobacteria can be seen. (d) In severe cases, the algal “crust” will need to be scarified or otherwise broken up to aid in recovery.

 

Management

Algae management combines a variety of cultural and chemical practices. Cultural practices are usually good when preventive measures can be put into place, but chemical control options are often recommended after algae is present.

 

Cultural

Improve soil drainage and aeration to discourage excessive algal growth. Avoid overirrigation and maintain proper moisture levels. Ensure proper nutrition levels for the turfgrass. Increase mowing height to promote turfgrass growth and reduce conditions favorable for algal growth. Enhance air movement and sunlight penetration by removing trees and shrubs as needed. Phosphorous applications have shown to increase algae severity, whereas acidifying fertilizers like ammonium sulfate have been show to suppress the organism with repeated applications.

 

Credit: John Kaminski/Penn State University

 

Figure 15.2.3: Results of a study conducted by Dr. Kaminski in which ammonium sulfate reduced algae populations, whereas fertilizer containing phosphorus exacerbated the problem. The left side of the test field was treated with ammonium sulfate, and shows significantly reduced algal growth compared to the right side, which was treated with a 20-20-20 fertilizer mix.

 

 

Chemical

Fungicides such as chlorothalonil, mancozeb, and potassium phosphite can be used to prevent or control algal growth. Chlorothalonil and macozeb are more effective when curative suppression is required.